* Do not derive from unittest.TestCase (not needed for pytest)
* assertRaises -> pytest.raises
* Simplify test_empty_dmatrix with test parametrization
* setUpClass -> setup_class, tearDownClass -> teardown_class
* Don't import unittest; import pytest
* Use plain assert
* Use parametrized tests in more places
* Fix test_gpu_with_sklearn.py
* Put back run_empty_dmatrix_reg / run_empty_dmatrix_cls
* Fix test_eta_decay_gpu_hist
* Add parametrized tests for monotone constraints
* Fix test names
* Remove test parametrization
* Revise test_slice to be not flaky
* Modin DF support
* mode change
* tests were added, ci env was extended
* mode change
* Remove redundant installation of modin
* Add a pytest skip marker for modin
* Install Modin[ray] from PyPI
* fix interfering
* avoid extra conversion
* delete cv test for modin
* revert cv function
Co-authored-by: ShvetsKS <kirill.shvets@intel.com>
Co-authored-by: Hyunsu Cho <chohyu01@cs.washington.edu>
